DIY Electrofisher Batteries

How to make your own Smith-Root-compatible electrofisher battery

If you’ve done any work involving fishes in streams, estuaries, lakes, or really any shallow body of water, you’re probably familiar with the Smith-Root LR-20B and LR-24 backpack electrofishers. These battery-powered units are used for research and management around the world. In addition to being rugged and reliable they include such luxuries as safety stops and digital displays.

Unlike the gas-generator-welded-to-a-packframe constructions that preceded them, battery powered electrofishers are quiet, relatively light, and easy to maintain. The only drawback is one shared by all battery powered equipment. Namely, that batteries don’t last forever. In fact, the standard lead-acid battery (the chemistry used in Smith-Root’s batteries) lasts for about five years if treated well. Heavy use, deep discharges, or long periods without maintenance charging can greatly reduce this lifespan. Even newer battery technologies, such as the lithium iron phosphate cells that Smith-Root recently introduced, share this limitation.

Beyond wearing out it’s also just convenient to have some spare batteries lying around. Whether you’re planning a week-long backpacking trip to shock some remote lakes or simply hedging your bets and not relying on the last user to charge everything up after they’ve finished their work, spare batteries can save your day in the field.

Smith-Root understands this and, conveniently, sells replacement batteries. However, at time of writing the basic 24V 7Ah battery retails for about $330.00USD. This isn’t much of a problem if you’ve got good funding, but for a grad student, a small lab, or a group doing educational outreach, $300 can be a lot of money. Luckily, it turns out that there’s a way around this.

A little while ago, one of my colleagues asked me to take a look at an old Smith-Root backpack electrofisher and batteries that they’d inherited from another group. The electrofisher was fine but the batteries were, predictably, shot. When asked if I could come up with a replacement I made dubious noises until I took a closer look and realized that each battery is simply made from a handful of off-the-shelf parts, a little glue, and a bit of solder. How much do these parts cost? About $30 for a standard battery and closer to $40 for a 24V 12A extended life battery ($388USD retail, at time of writing).

So I set out to make a few of my own and, if you’ve got a couple hours time and some basic tools, I’d be happy to show you how to do it too.